Placoderm
/ˈplækəˌdɜːrm/noun
An extinct armoured fish of the Silurian and Devonian, with bony plates over the head and shoulders.
The Greek roots
Literally: “plate skin”
The story of the word
Plate-skinned, and the plates are the whole point: these fish wore a hinged bony shield over the head and trunk and dominated Devonian water. Dunkleosteus, the largest, sheared with sharpened bone plates instead of teeth and is estimated at four metres or more, with estimates still being revised. Whether all later jawed vertebrates descend from inside this group is argued over every few years. One placoderm from Western Australia preserves an embryo still joined by an umbilical cord, the oldest known evidence of live birth in a vertebrate.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 19th century
Same family
In a sentence
The slab held the head shield of a placoderm and nothing else.
Placoderms had jaws before anything had teeth worth the name.